MRI-only based radiation therapy of prostate cancer: workflow and early clinical experience

Figures & data

Figure 1. MRI-only based RT planning workflow. (a) Presents T1/T2*-weighted in-phase image used for sCT and (d) construction. (b) Illustrates T2-weighted image applied for target delineation (e). Part (c) shows the T1/T2/T2*-weighted image adopted for gold marker verification (f). Part (g) presents the final sCT used for dose calculation (h) and IGRT with CBCT localization. Part (i) shows AP substitute DRR generated from the sCT in case IGRT is based on planar localization.

Table 1. Patient age and Gleason scores of MRI only based on planning and reference (CT) groups with RT only (monotherapy) or with additional hormonal therapy (LHRH).

	Monotherapy		LHRH
	MRI based n = 25	CT based n = 25	MRI based n = 100	CT based n = 100
Age (y ) median (range)	74 (40–82)	69 (54–79)	73 (58–85)	69 (55–86)
Gleason 6, n (%)	12 (48%)	12 (48%)	6 (6%)	8 (8%)
Gleason 7, n (%)	13 (52%)	12 (48%)	68 (68%)	62 (62%)
Gleason 8–10, n (%)	0 (0%)	1 (4%)	26 (26%)	30 (30%)

Table 2. Reasons for requirement of additional CT acquisition for patients undergoing the MRI-only RT planning workflow.

Reason	n	Details
Gold seed markers were not identified	8	Appearance of one or more macro calcifications like the gold markers (n = 2) Uncertain visualization or suspicious location of a marker (n = 3) Only two markers were seen in MRI (n = 3, the CT verified that there were actually only two markers in the prostate)
Artifacts due to hip implant	5	Artefacts overlapping the prostate (n = 3) Verifying the exact location of the prosthesis (n = 2)
Obesity	2	Verifying correct patient body outline contour
Motion artifact	1

The required CT was acquired for 16 of 200 patients.