Quantifying the reduction of respiratory motion by mechanical ventilation with MRI for radiotherapy

Radiation Oncology

Table 1 Overview of MRI acquisitions and scanning parameters

Breathing control strategy		DIBH	FB/RB	PBH
MRI strategy		3D MRI	4D MRI	3D cine-MRI
Sequence type		BTFE	TSE	BTFE
Resolution	(mm³)	2.0 × 2.0 × 2.0	1.3 × 1.6 × 4.0	1.6 × 1.6 × 1.6
Field of view	(mm³)	450 × 400 × 240	400 × 306 × 49	450 × 400 × 240—280
Echo time	(ms)	1.36	50	1.26
Repetition time	(ms)	2.7	562	2.5
Flip angle	(deg)	20	90	20
Slice orientation		Coronal	Coronal	Coronal
Dynamic time	(s)	14	6.2	11.4–14.5
Water-fat shift	(pixels)	0.266	0.658	0.389

For each breathing control strategy a dedicated MRI sequence was used. Dynamic time is the scan time needed to acquire one 3D image. The field of view had to be expanded depending on each volunteer’s anatomy for the 3D cine-MRI acquisition; therefore the dynamic scan time varies between volunteers. Abbreviations: deep inspiration breath-holds (DIBH), free breathing (FB), regularized breathing (RB), prolonged breath-holding (PBH), Balanced Turbo Field Echo (BTFE), Turbo Spin Echo (TSE)

ISSN: 1748-717X