Optimised standards for mri technique in rectal cancer staging

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Best Practice for Rectal Cancer Staging

A Technical Guide: how to obtain high resolution MRI scans for staging

Rectal Cancer

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Checklist – do the scans you are reviewing meet the required standards?

1. T2Weighted images? 1. TR>3500ms, TE >80ms

2. Enough signal to noise? 1. At least 4 acquisitons, 7 minutes per sequence

3. Are the scans of adequate High resolution?1. Pixel size derived from field of view 160mm and matrix 256 2. Slice thickness 3mm giving a : 0.6mm x 0.6mm x 3mm = 1.1mm3 voxel

4. Adequate coverage?1. – high res scans extend at least 5cm above the top of tumour2. – any discontinuous deposits seen on sagittal view are also covered on high res axials

5. Scans at the correct angle?1. Axial scans through the tumour are perpendicular to the rectal wall2. For Low rectal cancer – additional scans parallel to anal canal

6. Image quality is not degraded by movement artefact? 1. Buscopan 20mg i.m.2. Saturation Bands – superior and anterior3. Firm coil placement with adequate abdominal compression

The Royal MarsdenHigh 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 ye s

echo train length 16 8

matrix 256 x256 256 x 256

phase encoding inferosuperior for oblique inferosuperior for oblique

direction coronal coronal

phase encoding anteroposterior fo oblique anteroposterior fo oblique

direction axial axial

no of acquisitions 6 4

flow compensation no no

saturation bands anterior and superior 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

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Sagittal T2w TSE• FOV 250

• RFOV 100%• 24 slices• 3/.0.4mm• Foldover direction AP• 2 rest slabs anterior & superior• TSE factor 23• TE 99• TR 4520• Matrix 320/512r• Scan % 100• NSA 2-4• Scan length 6mins

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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 160mm x 160mm with a 256 x 256 matrix

pixel size in mm = field of view/matrixvoxel size mm3 = pixel size x slice thickness

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High res vs non high res• 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 tumourNon-High resSame patient – T stage?

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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

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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

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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

The Royal MarsdenReduction 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

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Empty bladderUse of anti-spasmodics

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Peristalsis – use of antispasmodics

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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

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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.

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DWI has insufficient resolution to distinguish tumour from fibrosis

bа с d

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Fat Saturation and Contrast Enhancement Does not improve accuracy

Tumour and normal anatomy both enhance

and are not distinguished

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MDT choices and making best use of high resolution MRI

MRI based Selectionof patientsFor range treatments

Local excision

MRI and PET surveillanceDeferral of surgery

ChemoradiotherapyRestage:Timing of surgery

after CRT6 vs 12?

Biological agents and neoadjuvant chemotherapy for MRI EMVI

Further Therapy/Extended surgery

for mrCRM/low rectal

MRI T1/T2 NxEMS /TEMS

pre/post operative CRTMRI surveillance…

MRI Low rectal Stage 3 or 4

Post CRTyMRI TRG 1-2

MRI T3a/T3b N anyLow rectal stage 1/2 Primary TME Surgery: open v laparoscopic

MRI T3c/T3d N anyEMVI positive CRM safe

potential CRM unsafe

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Reporting Minimum StandardsBaseline assessment of Rectal cancer MRI report Primary tumour The primary tumour is demonstrated as an [ Annular | Semi-annular | Ulcerating | | Polypoidal | Mucinous] mass with a [nodular / smooth] infiltrating border. The distal edge of the luminal tumour arises at a height of [ ] mm from anal verge: The distal edge of the tumour lies [ ]mm [Above,at, below] the top of the puborectalis sling The tumour extends craniocaudally over a distance of [ ] mm The proximal edge of tumour lies [above at below] the peritoneal reflection Invading edge of tumour extends from [ to ] O’clock Tumour is [confined to] [extends through] the muscularis propria: Extramural spread is [ ] mm mrT stage: [T1 ] [ T2 ] [ T3a <1mm] [ T3b 1-5mm ] [ T3c>5mm <15mm] [ T3d> 15mm ] [T4visceral ] [T4 peritoneal] Tumour is [present] [not present] the level of the puborectalis sling at this level: [Tumour is confined to the submucosal layer/part thickness of muscularis propria indicating that the intersphincteric plane/mesorectal plane is safe and intersphincteric APE or ultra low TME is possible] [Tumour extends through the full thickness of the muscularis propria : intersphincteric plane/mesorectal plane is unsafe, Extralevator APE. is indicated for radial clearance] [Tumour extends into the intersphincteric plane : intersphincteric plane/mesorectal plane is unsafe, therefore an extralevator APE. is indicated for radial clearance] [Tumour extends into the external sphincter : intersphincteric plane/mesorectal plane is unsafe.] [ Tumour extends into adjacent [prostate/vagina/bladder/sacrum] : exenterative procedure will be required Additional comments: .

Lymph node assessment Only benign reactive and no suspicious nodes shown [N0] [ ] mixed signal/irregular border nodes [N1/N2] Extramural venous invasion: [ No evidence ] [ Evidence] [ ] Small [ ]Medium [ ]Large vein invasion is present CRM The closest circumferential resection margin is at o’clock The closest CRM is from [Direct spread of tumour] [Extramural venous invasion] [Tumour deposit] Minimum tumour distance to mesorectal fascia: mm [CRM clear ] [CRM involved: Beyond TME surgery required] Peritoneal deposits: [ No evidence] [ Evidence] Pelvic side wall lymph nodes: [ None] [ Benign] [ Malignant mixed signal/irreg border] Location: [Obturator fossa • R •L ] . [External Iliac Nodes • R •L] .[ Internal iliac • R •L ] Summary: MRI Overall stage: T N M [mr TME plane CRM clear] , [ mr TME plane CRM involved ] , [ EMVI positive] [EMVI negative],[PSW positive ] [PSW negative] No adverse features eligible for primary surgery High risk (>T3b, EMVI pos, safe margins) for preoperative therapy : eligible for Serenade, Marvel, Trigger Poor prognosis unsafe margins eligible for preoperative chemoradiotherapy: eligible for Trigger trial Low Rectal <6cm – eligible for the Low Rectal Study.

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Post Treatment Assessment MRI Rectal Cancer Comparison is made with the previous examination of: • The treated tumour: shows no fibrosis,TRG5 • Less than <25% fibrosis, predominant tumour signal, TRG4 • 50% tumour/fibrosis, TRG 3 •>75% fibrosis, minimal tumour signal intensity,TRG2 •low signal fibrosis only no intermediate tumour signal TRG1 The distal edge of the luminal tumour arises at a height of [ ] mm from anal verge: The distal edge of the tumour lies [ ]mm [Above, at, below] the top of the puborectalis sling compared with []mm previously The tumour extends craniocaudally over a distance of [ ] mm compared with [ ]mm previously The proximal edge of tumour lies [above at below] the peritoneal reflection The invading edge of treated tumour extends from [ to ] O’clock Tumour signal is [Confined to / Extends through the muscularis propria.] Fibrotic signal is [ Confined to / Extends through muscularis propria.] Extramural spread: [ ]mm for tumour signal [ ]for fibrotic stroma yMR T stage: • T1 • T2 • T3a • T3b • T3c • T3d •T4 visceral •T4 peritoneal Treated tumour [is/ is not] present at or below the puborectalis sling • tumour signal/fibrosis extends into the submucosal layer/part thickness of muscularis propria : intersphincteric plane/mesorectal plane is safe intersphincteric APE or ultra low TME possible, CRM is safe • tumour signal/fibrosis extends through the full thickness of muscularis propria : intersphincteric plane/mesorectal plane is unsafe, for extralevator APE. • tumour signal/fibrosis extends into external sphincter : intersphincteric plane/mesorectal plane is unsafe:for extralevator APE •tumour signal/fibrosis extends into beyond external sphincter into [prostate/vagina ] : intersphincteric plane / mesorectal plane is unsafe, for extralevator APE.

Lymph nodes: • None /Only benign reactive [N0] • Present number mixed signal/irregular border [N1/N2] Extramural venous invasion: [• No evidence • Evidence] [• Small • Medium • Large] CRM Closest circumferential resection margin: [ ]O’clock Closest CRM is from [ Direct spread of tumour • Extramural venous invasion • Tumour deposit] Minimum tumour distance to mesorectal fascia: [ ]mm [ • CRM clear • CRM involved] Peritoneal deposits: [• No evidence • Evidence ] Pelvic side wall lymph nodes: • None • Benign • Malignant [Location: Obturator fossa • R •L . External Iliac Nodes •R •L. Inf Hypogastric •R •L ] Summary: y MRI Overall stage ymrT ymr N M , TRG • Low/intermediate risk, CRM clear, TRG 1-2, EMVI negative • High prognosis, CRM pos or TRG4/5 or EMVI positive TRG1-2 low tumour – eligible for consideration for deferral of surgery

Reporting Template Post Treatment

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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

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Key Bioimaging markers for poor outcome at baseline and post CRT

• 1mm TME plane CRM involvement on MRI• Depth of T extramural spread >5mm• Presence of MRI detected contiguous or discontinuous

venous invasion or vascular (non-nodal) tumour deposits• MRI detected mucinous tumours• Tumour spread into or beyond the intersphincteric plane• MRI TRG status

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Features that have no adverse prognostic significance on MRI

• >1mm distance of tumour to TME CRM plane on MRI

• mrT2 versus mrT3a <1mm spread• Depth of T extramural spread <5mm• MRI detected lymph nodes • MRI detected lymph nodes close to the mesorectal

fascia

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Jan 2016 course details please email : [email protected]

Venue: Royal Society of Medicine