MRI: techniques for rectal cancer staging and standardisation Gina Brown Department of Radiology Royal Marsden Hospital Imperial College, London

High resolution parameters   Phillips/Siemens 1.5T GE 1.5 T TR 5000 3025 TE 100 85 no of slices 20 25 slice thickness/gap 3 /0 .3 3 /0 interleaved ye s echo train length 16 8 matrix 256 x256 256 x 256 phase encoding inferosuperior for oblique direction coronal anteroposterior fo oblique axial no of acquisitions 6 4 flow compensation no saturation bands anterior and superior sequence Turbo Spin-echo FRFSE-XL NPW/ SCIC/ TRF/fast/ options no phase wrap ZIP512 scan duration 7 mins 5 to 7 minutes

Sagittal T2w TSE FOV 250 RFOV 100% 24 slices 3/.0.4mm Foldover direction AP 2 rest slabs anterior & superior TSE factor 23 TE 125 TR 3961 Matrix 320/512r Scan % 100 NSA 4 Scan length 6mins

1. Ensure scans are T2 weighted high resolution field of view and matrix parameters should not exceed a pixel size of 0.6mm x 0.6mm Either 200mm x 200mm with 384 x 384 matrix Or 60mm x 160mm with a 256 x 256 matrix pixel size in mm = field of view/matrix voxel size mm3 = pixel size x slice thickness

High res vs non high res High res –showing Early T2 tumour the difference between a high resolution and suboptimal MRI scan. The difference in technique can make a subtantial but entirely preventable difference to staging accuracy. High res –showing Early T2 tumour Non-High res Same patient – T stage?

2. Ensure planes are correct Phased array Coil positioning critical High Res Axials perpendicular to rectal wall Coronal imaging parallel to anal canal Don’t forget nodes Brown et al BJR 2005

Correct Scan planes Scans should be obtained perpendicular to the rectal wall, the sagittal MRI scans are used to plan the oblique axial images Coronal images should be undertaken parallel to the anal canal to visualise the distal anorectum and distal mesorectal plane High resolution coverage should include at least 5cm above the top of the tumour and to the L5/S1 level for all tumours to ensure that discontinuous tumour deposits are visualised

3. Use of Sat Bands and firm abdominal compression to limit abdominal wall motion The use of anterior and superior saturation bands reduce image degradation due to abdominal wall motion and  hyoscine butylbromide given as an i.m. injection or oral mebeverine reduces small bowel peristalsis respectively Without Sat Bands With Sat Bands

Reduction of physiological motion Good lower abdominal compression esp in thin patients Use of saturation bands / REST Slabs If phase AP Swap Phase direction R-L

Empty bladder Use of anti-spasmodics

Peristalsis – use of antispasmodics

4. Correct Coil Position The surface phased array coil should be placed correctly over the lower pelvis. For low rectal cancers the distal edge of the coil should lie 10cm below the symphysis pubis to ensure that the distal rectum is in the centre of the image

5. Other Sequences? T1 weighted imaging, contrast enhanced imaging and fat saturated sequences do not contribute and worsen staging accuracy and should not be used for primary rectal cancer staging. Caution when using diffusion weighted imaging for rectal cancer as it does not improve accuracy when compared with high resolution MRI techniques. The prolonged examination time caused by additional non-contributory sequences reduce the overall quality of the examination as well as prolonging patient discomfort.

DWI has insufficient resolution to distinguish tumour from fibrosis а с d

Fat Saturation and Contrast Enhancement Does not improve accuracy Tumour and normal anatomy both enhance and are not distinguished

MDT choices and making best use of high resolution MRI Local excision EMS /TEMS pre/post operative CRT MRI surveillance… MRI T1/T2 Nx MRI based Selection of patients For range treatments MRI T3a/T3b N any Low rectal stage 1/2 Primary TME Surgery: open v laparoscopic MRI T3c/T3d N any EMVI positive CRM safe Biological agents and neoadjuvant chemotherapy for MRI EMVI Chemoradiotherapy Restage: Timing of surgery after CRT 6 vs 12? Further Therapy /Extended surgery for mrCRM/low rectal potential CRM unsafe MRI Low rectal Stage 3 or 4 Post CRT yMRI TRG 1-2 MRI and PET surveillance Deferral of surgery

Reporting Minimum Standards

Reporting Template Post Treatment

Technique Summary of Essentials Scan duration = quality 7mins average length of each sequence 4-6 NSA/NEX and T2- FSE / TSE /FRFSE 0.6mm x 0.6mm x 3mm = 1.1mm3 voxel Adequate coverage – 5cm above top of tumour Perpendicular to the rectal wall Low rectal cancer – parallel to anal canal Ensure discontinuous deposits are covered on high res Buscopan Saturation Bands Firm coil placement with secure abdominal compression

Key Bioimaging markers for poor outcome at baseline and post CRT CRM involvement on MRI Depth of extramural spread >5mm Presence of MRI detected venous invasion MRI detected mucinous tumours Tumour spread into or beyond the intersphincteric plane MRI TRG status

10th – 11th March 2016, London, UK Intensive Hands On 2 Day Workshop Email: Gina.Brown@rmh.nhs.uk To receive further details 10th – 11th March 2016, London, UK Intensive Hands On 2 Day Workshop How to perform Rectal MRI staging and restaging accurately and consistently HANDS ON Workstation PRACTICE Cases Case Discussions Tips and tricks for : Reporting and MDT based working