Development and validation of a four-dimensional registration technique for DCE breast MRI

Insights into Imaging

Table 1 Description of numerical ranking scale and motion categories

NRS	Motion category		Motion pattern description
0	0	No motion	No motion
1	1	Mild motion	Delicate budging
2			Discreet, yet progressive jolt or small budging
3			Relevant, progressive budging
4	2	Moderate motion	Shift between t0 and t1, relevant subtraction artifacts
5			Moderate unilateral motion
6			Significant unilateral shift and/or rotational component
7			Large t0–t1 shift, substantial subtraction artifacts
8	3	Severe motion (nondiagnostic image quality)	Rugged distortions, tumors possibly not detectable
9			Extensive lateral/rotational motion with artifacts
10			Maximum and extensive distortions

Intrasequence motion was assessed on a numerical ranking scale and assigned to one of four motion categories. Use of this ranking scale ensures quantifiability and reproducibility of subjective assessment of motion, both before and after registration. Steps on the NRS are described by typical examples of respective motion patterns. t0–t1 shift refers to disproportionately strong motion between the unenhanced time point [t0] and the first postcontrast time point [t1]
NRS Numerical ranking scale