title: Rectal tumour volume (GTV) delineation using T2-weighted and diffusion-weighted MRI: Implications for radiotherapy planning.
abstract: OBJECTIVE
  To compare the rectal tumour gross target volume (GTV) delineated on T2 weighted (T2W MRI) and diffusion weighted MRI (DWI) images by two different observers and to assess if agreement is improved by DWI.
  
  
  METHODS
  27 consecutive patients (15 male, range 27.1-88.8 years, mean 66.9 years) underwent 1.5T MRI prior to chemoradiation (45Gy in 25 fractions; oral capecitabine 850mg/m(2)), including axial T2W MRI (TR=6600ms, TE=90ms) and DWI (TR=3000ms, TE=77ms, b=0, 100, 800s/mm(2)). 3D tumour volume (cm(3)) was measured by volume of interest (VOI) analysis by two independent readers for the T2W MRI and b800 DWI axial images, and the T2W MRI and DWI volumes compared using Mann-Whitney test. Observer agreement was assessed using Bland-Altman statistics. Significance was at 5%.
  
  
  RESULTS
  Artefacts precluded DWI analysis in 1 patient. In the remaining 26 patients evaluated, median (range) T2W MRI MRI and DWI (b=800s/mm(2)) 3D GTVin cm(3) were 33.97 (4.44-199.8) and 31.38 (2.43-228), respectively, for Reader One and 43.78 (7.57-267.7) and 42.45 (3.68-251) for Reader Two. T2W MRI GTVs were slightly larger but not statistically different from DWI volumes: p=0.52 Reader One; p=0.92 Reader Two. Interobserver mean difference (95% limits of agreement) for T2W MRI and DWI GTVs were -9.84 (-54.96 to +35.28) cm(3) and -14.79 (-54.01 to +24.43) cm(3) respectively.
  
  
  CONCLUSIONS
  Smaller DWI volumes may result from better tumour conspicuity but overall observer agreement is not improved by DWI.
authors.affiliation: Department of Radiology,Guy's & St Thomas' NHS Foundation Trust, London, UK; Department of Experimental and Clinical Biomedical Sciences - Radiodiagnostic Unit 2 - University of Florence- Azienda Ospedaliero-Universitaria Careggi, Firenze, Italy. Electronic address: francesco.regini@yahoo.it.
authors.forename: F
authors.initials: F
authors.lastname: Regini
authors.affiliation: Department of Radiology,Guy's & St Thomas' NHS Foundation Trust, London, UK; Division of Imaging Sciences & Biomedical Engineering, King's College London, King's Health Partners, St. Thomas' Hospital, London, UK. Electronic address: sofia.gourtsoyianni@gstt.nhs.uk.
authors.forename: S
authors.initials: S
authors.lastname: Gourtsoyianni
authors.affiliation: Department of Radiology,Guy's & St Thomas' NHS Foundation Trust, London, UK. Electronic address: rafaelgoiein@gmail.com.
authors.forename: R
authors.initials: R
authors.lastname: Cardoso De Melo
authors.affiliation: Division of Imaging Sciences & Biomedical Engineering, King's College London, King's Health Partners, St. Thomas' Hospital, London, UK; Medical Physics, Guy's & St Thomas' NHS Foundation Trust, London, UK. Electronic address: geoff.charles-edwards@kcl.ac.uk.
authors.forename: G D
authors.initials: GD
authors.lastname: Charles-Edwards
authors.affiliation: Department of Radiology,Guy's & St Thomas' NHS Foundation Trust, London, UK; Division of Imaging Sciences & Biomedical Engineering, King's College London, King's Health Partners, St. Thomas' Hospital, London, UK. Electronic address: nyree.griffin@gatt.nhs.uk.
authors.forename: N
authors.initials: N
authors.lastname: Griffin
authors.affiliation: Department of Radiology,Guy's & St Thomas' NHS Foundation Trust, London, UK. Electronic address: jyoti.parikh@gstt.nhs.uk.
authors.forename: J
authors.initials: J
authors.lastname: Parikh
authors.affiliation: Department of Radiology,Guy's & St Thomas' NHS Foundation Trust, London, UK. Electronic address: giles.rottenberg@gstt.nhs.uk.
authors.forename: G
authors.initials: G
authors.lastname: Rottenberg
authors.affiliation: Department of Clinical Oncology, Guy's & St Thomas' NHS Foundation Trust, London, UK. Electronic address: martin.leslie@gstt.nhs.uk.
authors.forename: M
authors.initials: M
authors.lastname: Leslie
authors.affiliation: Department of Clinical Oncology, Guy's & St Thomas' NHS Foundation Trust, London, UK. Electronic address: andrew.gaya@gstt.nhs.uk.
authors.forename: A
authors.initials: A
authors.lastname: Gaya
authors.affiliation: Department of Radiology,Guy's & St Thomas' NHS Foundation Trust, London, UK; Division of Imaging Sciences & Biomedical Engineering, King's College London, King's Health Partners, St. Thomas' Hospital, London, UK. Electronic address: vicky.goh@kcl.ac.uk.
authors.forename: V
authors.initials: V
authors.lastname: Goh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008875:Middle Aged; D015588:Observer Variation; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012004:Rectal Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D047368:Tumor Burden
keywords: Diffusion weighted imaging; MRI; Radiotherapy; Rectal cancer; Volumetry