Table 2.
Contour delineation on MRI for rectal cancer
| Reference | No of patients | Structures contoured | Method | MR sequence | Results |
| 12 | 10 | GTV (entire rectal wall at level of tumour) | MRI v CT (MR <2–3/52 from CT) one radiologist |
T 2W sagittal | CT overestimated all tumour radiological parameters Mean MRI GTV volume 18 cm3 smaller than on CT p < 0.05 Mean MRI GTV length, max width and distance of proximal tumour to anal verge significantly less than on CT (mean reduction 3.2 cm, 0.5 cm, 2.9 cm respectively) p < 0.05 |
| 21 | 15 | GTV | MRI V CT 1x radiologist in consultation with 1x radiation oncologist |
T 2 axial | Mean CT-GTV/ MRI- GTV volume ratio was 1.2cc (range 0.5–2.9) CT-GTV coverage inadequate for tumours with sigmoid or anal invasion and in the two cases this occurred there was significant underestimation of GTV on CT. |
| 14 | 24 | GTV | MRI T
2
v
s DWI Interobserver variation three radiation oncologists |
T
2W, DWI and a combination of both axial |
T
2 GTV volumes significantly larger than on DWI (approx. 2–3 x larger) No significant difference between observers per modality (mean conformity index 0.7 for T 2W and 0.71 for DWI) Mean distance between contours T 2 = 1.8 mm and DWI = 1.5 mm |
| 22 | 27 | GTV | MRI T
2W v
s DWI Interobserver variation two radiologists |
T 2W v s DWI axial |
T
2W MRI GTVs were slightly larger but not statistically different from DWI volumes Inter observer mean difference in volume was not improved with DWI Mean difference and 95% limits of agreement for T2W MRI and DWI GTVs were -9.8 (-55 to 35) cm3 and -14.8 (-54 to 24.4) cm3 respectively. |
| 23 | 50 | GTV | MRI pre- and post-CRT Interobserver variation two radiologists Histology reference standard for post-CRT radiology |
Pre- and Post-CRT DWI and T 2W MRI axial | Pre CRT MRI; Interobserver agreement for T
2W and DWI was excellent (ICC 0.97) ICC all modalities; pre-CRT 0.91–0.96 and post-CRT 0.61–0.79 ROC for post-CRT volume T 2W = 0.7, DWI = 0.93 and ADC = 0.54 |
CRT, chemoradiotherapy; DWI, diffusion weighted imaging; GTV, gross tumour volume; ICC, intraclass correlation coefficient; ROC, receiver operating characteristic.