Hit or Miss: Is there a role for CT/MRI fusion in Sarcoma radiotherapy planning? - PowerPoint PPT Presentation

1 / 45
About This Presentation
Title:

Hit or Miss: Is there a role for CT/MRI fusion in Sarcoma radiotherapy planning?

Description:

... intraobserver variation with fusion ... Does Fusion improve consistency within observers (intraobserver variation) ... More Interobserver Variation with CT ... – PowerPoint PPT presentation

Number of Views:99
Avg rating:3.0/5.0
Slides: 46
Provided by: PHS488
Learn more at: http://www.ctos.org
Category:

less

Transcript and Presenter's Notes

Title: Hit or Miss: Is there a role for CT/MRI fusion in Sarcoma radiotherapy planning?


1
Hit or Miss Is there a role for CT/MRI fusion in
Sarcoma radiotherapy planning?
  • Paris-Ann Gfeller

B.C. Cancer Agency, Vancouver, Canada
Musculoskeletal Tumour Group C. Candish, K.
Goddard, C. Grafton, L. Weir
2
Outline
  • Background
  • Study Design
  • Results
  • Conclusions

3
BackgroundSarcoma Radiotherapy Planning
  • The delineation of tumor from normal tissues is
    critical to the radiotherapy planning process
  • In Sarcoma treatment planning, improper
    delineation of tumour can lead to
  • Over-treatment of normal tissues
  • Severe late effects of treatment
  • (fibrosis, fracture, edema)
  • Under-treatment of tumour
  • Tumour recurrence

4
BackgroundSarcoma Radiotherapy Planning
  • Appropriate imaging is essential to properly
    delineate tumour volumes
  • Majority of current radiotherapy planning systems
    are CT based
  • With CT images alone it can be difficult to
    differentiate between tumor and normal tissue
  • Sarcomas are routinely imaged using MRI
  • MRI correlates with tumour extent and invasion
    into local structures
  • MRI shows peritumoral edema, which is included as
    part of target volume

5
BackgroundCT vs. MRI
Tumour is better defined by MRI compared to CT
MRI
CT
6
BackgroundHow Can We Combine CT and MRI?
By co-registering (fusing) CT and MRI images,
Radiation Oncologists can contour on CT and MRI
simultaneously, using imaging information from
both modalities
MRI
CT
7
BackgroundHow is Fusion Done?
CT
MRI-Fusion
8
BackgroundCT/MRI Fusion for Sarcomas?
  • There are no published studies describing the use
    of CT/MRI
  • Fusion for sarcoma treatment
  • CT/MRI Fusion studies in other tumor sites have
    shown
  • Improved tumor delineation with fusion
  • More accurate representation of gross disease
  • Decreased interobserver, intraobserver variation
    with fusion
  • More reproducible
  • Is there a benefit for CT/MRI fusion in sarcoma
    radiotherapy planning?

9
Study Questions?
  • Is CT-MRI Fusion useful in sarcoma planning?
  • Does Fusion alter the tumour volumes?
  • Does Fusion improve consistency between observers
    (interobserver variation)?
  • Does Fusion improve consistency within observers
    (intraobserver variation)?
  • Is CT/MRI fusion felt to be valuable to the
    planning process?
  • Radiation Oncologists opinion
  • Radiation Therapists opinion

10
Study Design
  • In 2004 a BCCA protocol was developed for fusion
  • sarcoma patients
  • Coordination of planning CT and MRI on the same
    day, in treatment position, with an
    immobilization device
  • Best MRI image series selected in consult with
    radiology and fused with a planning CT

11
Study Design
  • 19 patients were planned and treated from May
    2004 to February 2005 at Vancouver Cancer Centre
    (BCCA) with the CT-MRI fusion protocol
  • Identified all patients who had been treated
    according to protocol
  • Excluded patients who had received chemotherapy
    or surgery prior to radiation planning
  • Excluded tumours located in the thorax or head
    and neck
  • 9 patients met study criteria
  • 6 patients treated preoperatively, 3 patients
    had radiotherapy as definitive treatment
  • 5 MFH, 3 Fibromatosis, 1 Liposarcoma

12
Study Design
  • Original non-contrast planning CT images and
  • MRI images retrieved and then co-registered to
    produce CT/MRI fusion images
  • 2 image sets for each patient created
  • CT image set
  • CT/MRI fusion image set

13
Study Design
3 Radiation Oncologists (ROs)
9 CT Image Sets 9 Patient Summaries Contour
tumour volumes Complete Survey
9 Fusion Image Sets, 9 Patient Summaries Contour
tumour volumes Complete Survey
54 Image Sets Volumes Analyzed for Difference in
Mean Volumes Max/Min Ratio, X/Y/Z
Observers repeated contours on CT and Fusion for
Intraobserver ? Minimum 2 week delay between
contouring on image sets
14
RESULTS
15
ResultsMean Contoured Tumour Volume By Patient
CT volumes were 20 larger then fusion volumes
16
ResultsContoured Tumour Volumes
CT
Fusion
  • Oncologists included more NORMAL TISSUE if unsure
  • of volume on CT vs. MRI
  • This accounted for larger overall CT volumes

17
ResultsContoured Tumour Volumes
Fusion
CT
  • CT contours not always inclusive of MRI signal
    changes
  • GROSS TUMOUR EXCLUDED

18
Interobserver VariationMaximum Variation Ratio
Compare Max/Min Contoured Volume for each patient
between observers
  • More Interobserver Variation with CT

19
Interobserver VariationMaximum Variation Ratio
CT
Fusion
  • Volumes contoured with Fusion more consistent
    between observers

20
Intraobserver VariationMaximum Variation Ratio
Compare Max/Min Contoured Volume for each patient
within observers
  • More Intraobserver Variation with CT

21
ResultsContoured Tumour Volumes
  • Contoured Tumour Volumes (GTV)
  • Mean CT volumes by pt were larger then Fusion
    volumes
  • Mean CT gross tumour volumes for each patient
    were 1.2 times larger (range 0.90-1.56) then
    CT/MRI fusion images
  • p0.04
  • Interobserver Variation (Maximum Variation Ratio)
  • CT 3.72 (range 1.19- 9.0)
  • Fusion 1.72 (range 1.16-3.07)
  • Less interobserver variation with fusion p0.001
  • Intraobserver Variation (Maximum Variation Ratio)
  • CT 1.41 (range 1.03-1.72)
  • Fusion 1.10 (range 1.01-1.27)
  • Less intraobserver variation with fusion p0.02

22
ResultsSurvey
  • 10 question survey completed by Radiation
    Oncologists and Radiation Therapists involved in
    sarcoma planning after completing planning
  • Radiation Oncologists unanimously felt better
    able to delineate tumour from normal tissue with
    fusion
  • Radiation therapists felt fusion aided in their
    ability to prepare images (contour critical
    structures) in preparation for planning by
    Radiation Oncologists

23
Conclusions A Role for Fusion in Sarcoma
Planning?
  • One of first studies to formally evaluate use
    fusion for planning sarcomas
  • Results justify use of fusion
  • Fusion allows Radiation Oncologists to define
    smaller more accurate volumes which may
  • decrease dose to normal tissues
  • Improve tumour coverage
  • Fusion increases consistency and reproducibility
    of treatment planning
  • Results show the optimal modality for planning
  • sarcoma is CT-MRI Fusion to ensure gross disease
  • appropriately represented

24
Thank you
  • CTOS Abstract Review Committee
  • BCCA Musculoskeletal Tumour Group
  • Dr. C. Candish
  • Dr. K. Goddard
  • Dr. C. Grafton
  • Dr. L. Weir
  • Dr. C. Keogh (Radiology)
  • C. Marlowe, K. Dahle, C. Mengerink (Radiation
    Therapy)
  • V. Morovan (Statistics)

Imaging Matters
25
Questions?
26
Supplementary Slides
27
ResultsCT with Bowel Contrast
CT with Contrast
MRI
28
ResultsCT with IV Contrast
CT with Contrast
MRI
29
ResultsImaging and Registration
    Registration Error Registration Error
Patient  MRI Type avg error (cm) max error (cm)
1 T2FS 0.15 0.33
2 STIR 0.34 0.41
3 T1FS 0.28 0.61
4 T2FS 0.26 0.38
5 T2FS 0.31 0.63
6 T2FS 0.4 0.77
7 T2FS 0.57 0.79
8 T2FS 0.16 0.23
9 T2FS 0.28 0.45
    0.305556 0.511111
MRI slices 5mm
30
ResultsContoured Tumour Volumes
CT
Fuse
31
ResultsContoured Tumour Volumes PTVs
CT
Fuse
32
Results Underestimate Tumour Extent
33
ResultsContoured Tumour Volumes
34
ResultsGross Tumour Volumes by Observer
35
ResultsGross Tumour Volume By Patient
36
ResultsMean Gross Tumour Volume By Patient
  • CT volumes 1.2 times larger then fusion, p0.04

37
ResultsMean PTV By Patient
38
ResultsMeasuring Variation
39
ResultsMEAN X,Y,Z Variation
Standard Deviation smaller for fusion all
directions All dimensions smaller for Fusion
(sup/inf most significant)

  CT   Fusion  
  avg SD avg SD
med 3.74 1.12 3.63 0.4
lat -4.44 1.63 -4.28 0.4
     
ant 4.93 0.7 4.3 0.4
post -3.91 1.4 -3.78 0.6
     
sup 7.43 1.8 6.57 0.8
inf -7 2.36 -6.28 0.8
40
ResultsVariation Superior to Inferior
41
ResultsMedial and Lateral Variation
ct ct   fuse fuse
med lat   med lat
6 -5.5   5 -4
1 -1.5   1 -2
3 -2.67   3 -2
3.333 -6.33   5.2 -5
2 -2.67   0 -3.167
1.333 -1.83   1.3 -3
6 -6   5.5 -7.333
5 -5.5   4.7 -5
6 -8   7 -7
3.741 -4.44   3.6 -4.278
42
ResultsCompletion Survey
  • Survey completed for each image set at completion
    of contouring (N88)
  • Linear Analog Rating Scale
  • Rate the general quality of this CT (fusion)
    image set?
  • (1 poor, 5-meets expectations, 10 exceeds
    expectations)
  • CT score 4.9, Fusion 6.7
  • Both image sets were acceptable for contouring
  • Rate the quality of this CT (fusion) image set
    for delineating
  • (1- can not delineate to 10 exceeds
    expectations)
  • a. Tumor volume
  • CT 4.0, Fusion 7.8
  • b. Critical Structures
  • CT 4.2, Fusion 7.4

Indicates Subjectively Better" Delineation of
Tumour and Critical Structures with Fusion
43
ResultsRadiation Oncologists Completion Survey
  • Using a linear analog scale (poor to exceeds
    expectations)
  • rate the quality of this CT (fusion) image set
    for delineating
  • Tumour Volumes
  • CT 4.0, Fusion 7.8
  • Normal Tissues
  • CT 4.2, Fusion 7.4

Fuse
Fuse
CT
CT
poor meets expectations
exceeds
poor meets expectations
exceeds
Improved Delineation of Tumour and Normal
Structures with Fusion
44
ResultsRadiation Therapists Opinions
  • 8 question survey for Radiation therapists (n4)
    involved in sarcoma fusions
  • Average time for fusion
  • 35.5 minutes
  • Usefulness of Fusion for delineating normal
    structures
  • Extremely useful
  • Difficulty of Performing Fusions compared to
    other sites
  • Slightly more difficult, (extremities the most
    difficult)
  • Important factors in image fusion
  • Tumour location, MRI quality, time available
  • IMMOBILIZATION and Position

45
ConclusionsA Role for Fusion in Sarcoma Planning?
  • CT/MRI fusion is valuable to the planning process
    for sarcoma
  • Contoured Tumour Volumes
  • More normal tissue included in the target volumes
    with CT
  • Disease excluded on CT
  • Volume Variation
  • More consistency in contours with Fusion
  • Completion Survey
  • Radiation Oncologists and Therapists felt fusion
    was valuable
Write a Comment
User Comments (0)
About PowerShow.com