MR-guided proton therapy: a review and a preview

Radiation Oncology

Table 1 Overview of synthetic CT generation methods applied to patient data and evaluated for proton therapy dose calculations

Body site	Method	MRI pulse sequence	Conversion time	MAE in HU	Dose accuracy	Study
Brain	Voxel-based classification	2D TSE, 3D UTE	300 s	145	∆DVH < 2%	[15, 16]
Brain	Voxel-based classification	UTE, T₁w	n.a.	128	∆DVH < 2%	[17]
Brain	Voxel-based classification	T₁w, T₂w	205 s	124	∆DVH < 0.5 Gy Γ_2%2mm = 98%	[20]
Brain	Deep learning	T₁w	30 s	54	∆Range = 0.14 ± 1.11%	[48]
Brain	Deep learning	T₁w	2 s (2D) 12 s (3D)	82–135 (2D) 82–147 (3D)	Γ_2%2mm = 98% (2D) Γ_2%2mm = 97% (3D)	[49]
Brain Prostate	Voxel-based classification	T₁/T₂*w dual gradient echo	30 s	42 (brain)^a 34 (prostate)^a	∆DVH < 1.4% Γ_2%2mm = 99%	[18]
Prostate	Bulk assignment	3D dual spoiled gradient echo	120 s	83	∆DVH < 2%/2 Gy Γ_2%2mm = 98%	[19]
Prostate	Bulk assignment	3D dual spoiled gradient echo	120 s	81	Mean ∆DVH = 0.6%/1.5 Gy Γ_2%2mm = 93%	[50]
Abdomen Pediatric	Voxel-based classification	T₂w TSE	195 s	212 (bone) 125 (lung) 52 (soft tissue)	∆DVH < 4% Γ_2%2mm = 88%	[51]
Liver	Deep learning	T₁w	120 s	73	∆DVH < 1% Γ_2%2mm = 97%	[52]

Abbreviations: TSE turbo spin echo, UTE ultra-short echo time, T₁w T₁-weighted, T₂w T₂-weighted, ∆DVH change in dose-volume histogram parameters, Γ_2%2mm 2%, 2 mm gamma criterion, ∆Range change in proton range
^ain pre-selected regions of interest

ISSN: 1748-717X