ISO 16087:2013 手術用インプラント—整形外科用インプラントの移動を評価するためのレントゲンステレオ写真測量分析 | ページ 5

2.1

absolute movement

movement of a rigid body relative to a fixed reference rigid body

2.2

accuracy

closeness of agreement between a measured quantity value and a true quantity value of a measurand

2.3

bias

estimate of a systematic measurement error

2.4

biplanar technique

RSA technique where two X-ray cassettes/films/sensors are set at an angle to each other

2.5

calibration cage

calibration box

reference frame used to create a three-dimensional coordinate system, with definition of position and orientation, and to determine the position of the two roentgen foci

2.6

condition number

calculated number used to assess the distribution of markers

Note 1 to entry: High condition numbers indicate poor marker distribution, while low condition numbers indicate appropriate marker distribution.

Note 2 to entry: See Annex A, which establishes the methodology to determine the condition number associated with the marker distribution.

2.7

crossing line error

shortest distance between the two X-rays projecting the centre of a marker in the two RSA images

2.8

double examinations

two RSA examinations of the same patient within an interval of several minutes

2.9

helical axis

screw axis

instantaneous axis about which the decomposition of the motion of an object from one position to another has a translation along and a rotation about a single axis

2.10

marker

small diameter biocompatible metal sphere having a precise size and shape used as landmark

Note 1 to entry: Spherical tantalum markers serve as well-defined landmarks.

Note 2 to entry: The diameter is commonly ≤ 1 mm.

2.11

maximum total point motion

MTPM

length of the translation vector of the marker or virtual marker in a rigid body that has the greatest migration

Note 1 to entry: It can only have positive values, and is not normally distributed.

2.12

mean error of rigid body fitting

rigid body error

measure indicating the mean change of relative positions of markers (in the same object) over time compared to the initial, reference configuration

Note 1 to entry: Annex A establishes the methodology to determine the mean error associated with the change of relative positions of markers.

2.13

migration

change in position and orientation of an implant relative to the host bone assessed between follow-up examinations

2.14

model-based RSA

RSA technique in which the position and orientation of an implant is assessed by matching a virtual projection of a three-dimensional model of the implant to the actual radiographic projection of the implant

2.15

phantom

object that is used as a representative of an anatomical part

2.16

precision

degree to which repeated measurements under unchanged conditions show the same results

2.17

reference plate

planar object holding markers used for calibration of RSA-examinations by linking its two-dimensional coordinate system to the three-dimensional global coordinate system of previous RSA-examinations that were calibrated using a three-dimensional calibration cage

2.18

reference rigid body

rigid body that defines a fixed coordinate system, the origin of which is located in that rigid body’s geometrical centre

2.19

rotation matrix

mathematical expression of the three-dimensional rotation of a rigid body

2.20

RSA

roentgen stereophotogrammetric analysis

radiostereometry

radiostereometric analysis

roentgen stereophotogrammetry

measurement technique that relies on stereo X-ray images and can be used to assess relative changes in position and orientation of two rigid bodies (e.g. an orthopaedic implant and host bone) relative to each other

Note 1 to entry: In order to reach a high level of accuracy, markers are used as landmarks in the bone and a calibration object (calibration cage or reference plate) is used to assess the position of two synchronised X-ray sources in the global coordinate system defined by the calibration cage.

2.21

virtual marker

three-dimensional point from visible landmarks or calculated from known geometry to determine a specific point of an implant

Note 1 to entry: Virtual markers were formerly named fictive markers.

2.22

uniplanar technique

RSA technique where the two X-ray cassettes/films/sensors are in the same plane